1. Field of the Disclosure
This disclosure relates to an electrode for a fuel cell, a method of fabricating the same, and a membrane-electrode assembly for a fuel cell and a fuel cell system including the same.
2. Description of the Related Technology
A fuel cell is a power generation system for producing electrical energy through an electrochemical redox reaction between an oxidant and hydrogen from a hydrocarbon-based material such as methanol, ethanol, or a natural gas. Such a fuel cell includes a stack composed of unit cells, and which produces various ranges of power. Since the fuel cell has between about four and about ten times higher energy density than a small lithium battery, it may be used as a small portable power source. Representative examples of fuel cells include polymer electrolyte membrane fuel cell (“PEMFC”) and direct oxidation fuel cell (“DOFC”). A direct oxidation fuel cell configured to use methanol as a fuel is called a direct methanol fuel cell (“DMFC”). The PEMFC has an advantage of high energy density, but it also has problems including a need to carefully handle hydrogen gas and a requirement of accessory facilities, such as a fuel reforming processor for reforming methane, methanol, natural gas, and the like, to produce hydrogen as the fuel gas. The DOFC has lower energy density than that of the PEMFC, but it has advantages of easy handling of a fuel, being capable of operating at room temperature due to its low operation temperature, and no need for additional fuel reforming processors.
In the above-mentioned fuel cell systems, the stack that generates electricity generally includes several unit cells stacked adjacent to one another. Each unit cell is formed of a membrane-electrode assembly (“MEA”) and a separator (also referred to as a bipolar plate). The MEA is composed of an anode (also referred to as a “fuel electrode” or an “oxidation electrode”) and a cathode (also referred to as an “air electrode” or a “reduction electrode”) separated by a polymer electrolyte membrane. At least one of the anode and the cathode includes an electrode substrate and a catalyst layer. Further, the electrode substrate may be configured to transport gas or remove moisture. However, flooding and drying phenomena may occur in a MEA during driving under humidifying and non-humidifying conditions, so the water management balance is broken and may, therefore, cause performance deterioration of the fuel cell.